Disk drive device with structure that can suppress vaporization and diffusion of lubricant

ABSTRACT

A disk drive device comprises a chassis, an annular hub having an outer periphery on which a recording disk is to be mounted, and having an inner periphery to which an annular magnet is fastened, a fluid bearing unit that supports the hub in a manner freely rotatable relative to the chassis, an opposing wall formed annularly on the surface of the chassis at the hub side, and facing with at least partially the inner periphery of the hub in the radial direction, a first gap that extends in the axial direction between the inner periphery of the hub and the opposing wall, and a second gap that is continuous from the first gap and extends in the radial direction between the end face of the hub and the chassis.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a disk drive device including a fluiddynamic bearing unit.

2. Description of the Related Art

In recent years, disk drive devices, such as hard disk drives, generallyinclude a fluid dynamic bearing unit that enables a disk to stablyrotate at a fast speed. For example, JP 2008-275074 A discloses a motorincluding a dynamic bearing, and this motor has a lubricant filledbetween a sleeve forming a part of a stator, and a shaft forming a partof a rotor. Dynamic pressure generated in the lubricant supports therotor in a non-contact manner, thereby enabling a smooth fast-speedrotation.

Conversely, there is a demand for the disk drive devices to furtherincrease the recording capacity. An example technique to satisfy thisdemand is to increase the recording density.

In order to increase the recording density, a clearance between arecording/playing head and a disk surface may be reduced. When, however,this clearance is too narrow, it becomes difficult for therecording/playing head to precisely trace the tracks on the disk even aminute particle sticks on the disk surface, resulting in a read/writeerror. In the worst case, the recording/playing head is damaged, makingthe disk drive device inoperable.

One of the causes of such particles is a vaporization of the lubricantincluded in the fluid dynamic bearing unit due to a high-temperatureenvironment originating from a fast-speed rotation of the disk, i.e., afast-speed rotation of a motor. The vaporized lubricant diffuses in thedisk drive device, leaves a condensation on the disk surface, therebybeing deposited thereon.

In addition, with respect to the high-temperature environment,downsizing of the disk drive devices increases the temperature thereofin a use atmosphere, and there is a demand to enable the use of the diskdrive devices at a further high temperature, e.g., an atmospheretemperature of equal to or higher than 85 degrees.

Still further, there is a demand to ensure a longer lifetime which isequal to or longer than, for example, five years by elongating a timeuntil the lubricant is vaporized and dissipated.

The present invention has been made in view of the foregoingcircumstances, and it is an objective of the present invention toprovide a disk drive device which prevents a lubricant included in afluid dynamic bearing unit from being vaporized and diffusing, and whichenables a further increase in a recording capacity.

Moreover, it is another objective of the present invention to provide adisk drive device which suppresses a vaporization of the lubricantincluded in the fluid dynamic bearing unit to ensure a long lifetime.

SUMMARY OF THE INVENTION

To accomplish the above objective, a first aspect of the presentinvention provides a disk drive device that includes: a chassis; anannular rotator having an outer periphery to be engaged with a recordingdisk, and having an inner periphery fastened with an annular magnet; afluid bearing unit that supports the rotator in a manner freelyrotatable relative to the chassis; an opposing wall that is formedannularly on a surface of the chassis at the rotator side, and faceswith at least partially the inner periphery of the rotator in a radialdirection; a first gap running in an axial direction between the innerperiphery of the rotator and the opposing wall; and a second gapcontinuous from the first gap, and running in the radial directionbetween an end face of the rotator and the chassis.

To accomplish the above objective, a second aspect of the presentinvention provides a disk drive device that includes: a chassis; arotator that comprises a disk mount part, and an inner periphery towhich a ring-shape magnet is fastened; and a fluid bearing unit thatgenerates fluid dynamic pressure to a lubricant to support the rotatorin a freely rotatable manner relative to the chassis, in which: therotator comprises a rotator opposing face that faces with the chassis inan area outwardly in a radial direction with respect to an innerperiphery of the magnet; the chassis comprises a chassis opposing facethat faces with the rotator opposing face with a first opposing gap; anda gas dynamic pressure generating groove that generates, when therotator rotates relative to the chassis, dynamic pressure in a pump-indirection to gas present in the first opposing gap is provided in eitherone of the rotator opposing face and the chassis opposing face.

To accomplish the above objective, a third aspect of the presentinvention provides a disk drive device that includes: a chassis; arotator that comprises a disk mount part, and an inner periphery towhich a ring-shape magnet is fastened; and a fluid bearing unit thatgenerates fluid dynamic pressure to a lubricant to support the rotatorin a freely rotatable manner relative to the chassis, in which: therotator comprises a rotator opposing face that faces with the chassis inan area outwardly in a radial direction with respect to an innerperiphery of the magnet; the chassis comprises a chassis opposing facethat faces with the rotator opposing face with an opposing gap; a gasdynamic pressure generating groove that generates, when the rotatorrotates relative to the chassis, dynamic pressure in a pump-in directionto gas present in the opposing gap is provided in either one of therotator opposing face and the chassis opposing face; and the lubricantcontains an ionic liquid.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded perspective view illustrating a disk drive deviceaccording to an embodiment of the present invention;

FIG. 2 is a cross-sectional view taken along a line A-A in FIG. 1;

FIG. 3 is an enlarged cross-sectional view illustrating the proximalarea of a shaft body and that of a bearing body both in FIG. 2;

FIG. 4 is a pressure distribution diagram exemplarily illustrating adistribution of radial dynamic pressures of the disk drive device of theembodiment of the present invention;

FIG. 5 is a cross-sectional view illustrating a structure of a modifiedexample; and

FIG. 6 is a cross-sectional view illustrating a step for emitting inputlight to a lubricant to obtain output light.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of the present invention will be explained belowwith reference to the accompanying drawings. The same or correspondingstructural element and component illustrated in respective figures willbe denoted by the same reference numeral, and the duplicated explanationthereof will be omitted accordingly. The dimension of the componentillustrated in the respective figures is enlarged or scaled down asneeded to facilitate understanding to the present invention. Inaddition, a part of the component in the respective figures notimportant to explain the embodiments will be illustrated in an omittedmanner.

A disk drive device according to the embodiment is suitably applied as adisk drive device like a hard disk drive which has a magnetic recordingdisk that magnetically records data, and which rotates and drives such adisk.

For example, this disk drive device includes a rotating body that isattached to a stationary body in a freely rotatable manner via abearing. The rotating body includes a loader that can load thereon adrive-target media like a magnetic recording disk.

The bearing includes, for example, a radial bearing and a thrustbearing. As an example, the thrust bearing is located outwardly in theradial direction with respect to the radial bearing.

The radial bearing and the thrust bearing may be each a fluid bearingthat generates dynamic pressure to a lubrication medium present betweena shaft body and a bearing body.

Still further, this disk drive device includes a rotating driver thatapplies rotation torque to the rotating body. This rotating driver is,for example, a brush-less spindle motor. This rotating driver includes,for example, coils and a magnet.

For example, the disk drive device includes a dynamic pressuregenerating groove that generates fluid dynamic pressure to a gaseousbody when the rotating body rotates relative to the stationary body.

The dynamic pressure generating groove is provided in either one ofopposing faces of the rotating body and the stationary body facing witheach other with an opposing gap, and generates fluid dynamic pressure toa gaseous body present in such an opposing gap.

For example, the dynamic pressure generating groove is provided so as toencircle the fluid bearing.

[Embodiment]

FIG. 1 is a perspective view illustrating a disk drive device 100according to this embodiment. FIG. 1 illustrates a condition in which atop cover 22 is detached in order to facilitate understanding to thepresent invention. Components not important to explain this embodiment,such as a clamper and an electronic circuit, are omitted in FIG. 1. Thedisk drive device 100 includes a chassis 24, a shaft 110, a rotator(e.g., a hub) 26, magnetic recording disks 62, a data reader/writer 60,the top cover 22, a center screw 74, and for example, six peripheralscrews 104.

In the following explanation, a side at which the hub 26 is mountedrelative to the chassis 24 will be defined as an upper side. Inaddition, a direction along a rotation axis R of the rotating body, anarbitrary direction passing through the rotation axis R on a planeperpendicular to the rotation axis R, and an arbitrary direction on sucha plane will be defined as an axial direction, a radial direction, and aplanar direction, respectively. The notations of such directions are notto limit the posture of the disk drive device 100 when in use, and thedisk drive device 100 can be used in any arbitrary posture.

The magnetic recording disk 62 is, for example, a 2.5-inch magneticrecording disk having a diameter of 65 mm and formed of a glass, and, adiameter of a center hole thereof is 20 mm. If the magnetic recordingdisk 62 is made thin, the rigidity thereof decreases, and is warped whenpolished at the time of the manufacturing of the disk drive device 100,thereby reducing the processing flatness. Conversely, if the magneticrecording disk 62 is made thick, the weight increases. Regarding themagnetic recording disk 62, it is proven that if the thickness is withina range at least from 0.5 mm to 1.25 mm, the rigidity and the weight arepractical. In this embodiment, the magnetic recording disk 62 has athickness of from 0.7 mm to 0.9 mm, which suppresses a decrease of theprocessing flatness, thereby suppressing a reduction of the recordingdensity. For example, four magnetic recording disks 62 are to be mountedon the hub 26, and are rotated together with the rotation of the hub 26.As will be discussed later, the magnetic recording disks 62 are fastenedto the hub 26 by spacers 72 and a clamper 72.

The chassis 24 includes a bottom plate 24A that forms the bottom of thedisk drive device 100, and an outer circumference wall 24B formed alongthe outer periphery of the bottom plate 24A so as to surround an areawhere the magnetic recording disks 62 are to be mounted. For example,six screw holes 24C are provided in the top face of the outercircumference wall 24B.

The data reader/writer 60 includes an unillustrated recording/playinghead, a swing arm 64, a voice coil motor 66, and a pivot assembly 68.The recoding/playing head is attached to the tip of the swing arm 64,records data in the magnetic recording disk 62, or reads the datatherefrom. The pivot assembly 68 supports the swing arm 64 in aswingable manner to the chassis 24 around a head rotating shaft S. Thevoice coil motor 66 allows the swing arm 64 to swing around the headrotating shaft S to move the recording/playing head to a desiredlocation over the top face of the magnetic recording disk 62. The voicecoil motor 66 and the pivot assembly 68 are configured by aconventionally well-known technology of controlling the position of ahead.

The top cover 22 is a thin plate formed in a substantially rectangularshape, and has, for example, six screw through-holes 22C provided at theperiphery of the top cover 22, a cover recess 22E, and a center hole 22Dprovided at the center of the cover recess 22E. The cover recess 22E isprovided around the rotation axis R. The top cover 22 is formed by, forexample, pressing an aluminum plate or an iron-steel plate into apredetermined shape. A surface processing like plating may be applied onthe top cover 22 in order to suppress corrosion. The top cover 22 isfixed to the top face of the outer circumference wall 24B of the chassis24 by, for example, the six peripheral screws 104. The six peripheralscrews 104 correspond to the six screw through-holes 22C and the sixscrew holes 24C, respectively. In particular, the top cover 22 and thetop face of the outer circumference wall 24B are fixed with each otherso as to suppress a leak into the interior of the disk drive device 100from the joined portion of the top cover 22 and the top face of theouter circumference wall 24B. The interior of the disk drive device 100is, more specifically, a clean space 70 surrounded by the bottom plate24A of the chassis 24, the outer circumference wall 24B of the chassis24, and the top cover 22. This clean space 70 is designed so as to befully sealed, i.e., so as not to have a leak-in from the exterior and aleak-out to the exterior. The clean space 70 is filled with clean gashaving particles eliminated. Hence, foreign materials like the particlesare prevented from sticking to the magnetic recording disk 62 from theexterior of the clean space 70, thereby improving the reliability of theoperation of the disk drive device 100. The center screw 74 correspondsto a retainer hole 10A of the shaft 110. The top cover 22 is joined withthe shaft 110 by causing the center screw 74 to pass all the way throughthe center hole 22D and to engaged with the retainer hole 10A in a screwmanner.

FIG. 2 is a cross-sectional view taken along a line A-A in FIG. 1.

With reference to FIG. 2, a stationary body 2 further includes a shaftbody 6, a stator core 32, and coils 30. The shaft body 6 includes theshaft 110 and a shaft holder 112. The shaft 110 has a shaft flange 12provided at one-end side, i.e., at a side opposite to the shaft holder112. The shaft holder 112 includes a flange part 16 and a flangeencircling part 18.

A rotating body 4 includes the hub 26, a bearing body 8, a cap 48, and amagnet 28 in a cylindrical shape as viewed from the top. The rotatingbody 4 and the stationary body 2 include, as a lubrication medium, alubricant 20 continuously present in some gaps between the shaft body 6and the bearing body 8. The bearing body 8 includes a sleeve 42. Thesleeve 42 encircles the shaft 110, and may be referred to as a shaftencircling member in some cases.

The shaft body 6, the bearing body 8, and the lubricant 20 form a fluidbearing unit together with dynamic pressure generating grooves to bediscussed later.

The material of and the technique of forming the chassis 24 are notlimited to any particular ones. In this embodiment, as an example, thechassis 24 is shaped by die-casting of an aluminum alloy as a singlepiece. The chassis 24 may be formed by, for example, pressing of a sheetmetal, such as stainless steel or aluminum. In this case, the chassis 24has a part including an embossed face formed by pressing. The chassis 24may have a surface process layer like nickel plating. In addition, thechassis 24 may have a part formed of a resin. Still further, the chassis24 may have a coating layer like an epoxy resin. The bottom plate 24A ofthe chassis 24 may be formed by laminating equal to or greater than twosheets.

The chassis 24 has an opening 24D opened around the rotation axis R ofthe rotating body 4, and a protrusion 24E which encircles the opening24D and which is in a cylindrical shape as viewed from the top. Theprotrusion 24E protrudes toward the hub 26 from the upper face of thebottom plate 24A, and extends beyond the flange encircling part 18 ofthe shaft holder 112.

Still further, a recess 24N in an annular shape as viewed from the topis provided in the bottom plate 24A of the chassis 24 circularly aroundthe rotation axis R. This recess 24N is provided at a location facingwith a mount part 26J of the hub 26 to be discussed later in the axialdirection. In addition, in this embodiment, an opposing wall 24F in acircular shape as viewed from the top is provided on the bottom plate24A circularly around the rotation axis R. This opposing wall 24F isprovided at a location included in a projection area of the magnet 28 inthe axial direction in this embodiment. Moreover, the opposing wall 24Fis provided at a location facing with a part of the inner periphery ofthe hub 26 in the radial direction, and is continuous from the recess24N in a cross-sectional view in this embodiment.

A first gap 202 between the opposing wall 24F and the inner periphery ofthe hub 26 can be from 0.05 to 0.4 mm for example. The lower end face ofthe mount part 26J of the hub 26 faces with the upper face of the recess24N of the chassis 24 to form a second gap 204. The second gap 204 runsin the radial direction, and can be from 0.02 to 0.4 mm for example. Theouter periphery of the mount part 26J of the hub 26 faces with the innerperiphery of the recess 24N of the chassis 24 to form a third gap 206.The third gap 206 runs in the axial direction, and can be from 0.05 to0.4 mm for example. The lower end face of the magnet 28 faces with anextended face extended in the radial direction from the upper end of theopposing wall 24F of the chassis 24 to form a fourth gap 208. The fourthgap 208 runs in the radial direction, and can be from 0.02 to 0.5 mm forexample. In this embodiment, as an example, the first gap 202 is from0.1 to 0.3 mm, the second gap 204 is from 0.05 to 0.2 mm, the third gap206 is from 0.1 to 0.3 mm, and the fourth gap 208 is from 0.1 to 0.3 mm.

The first gap 202 has a dimension in the axial direction which is largerthan the dimension in the radial direction, and is, for example, equalto or greater than five times as much as the dimension in the radialdirection. In this case, the channel resistance of the first gap 202 canbe increased. The second gap 204 has a dimension in the radial directionwhich is larger than the dimension in the axial direction, and is, forexample, equal to or greater than five times as much as the dimension inthe axial direction.

In this case, the channel resistance of the second gap 204 can beincreased. The third gap 206 has a dimension in the axial directionwhich is larger than the dimension in the radial direction, and is, forexample, equal to or greater than five times as much as the dimension inthe radial direction.

In this case, the channel resistance of the third gap 206 can beincreased. When the gap is small, depending on a manufacturing error, arotating part may hit a non-rotating part. Hence, it is desirable thatthe respective dimensions in the axial direction of the first gap 202and the third gap 206 should be equal to or smaller than 50 times asmuch as the respective dimensions in the radial direction. In addition,it is desirable that the dimension in the radial direction of the secondgap 204 should be equal to or smaller than 50 times as much as thedimension in the axial direction.

The hub 26 includes a hub opposing face that faces with the chassis 24in an area outwardly in the radial direction with respect to the innerperiphery of the magnet 28, while the chassis 24 has a chassis opposingface that faces with the hub opposing face with an opposing gap. A gasdynamic pressure generating groove that generates dynamic pressure in apump-in direction to the gas present in the opposing gap when the hub 26rotates relative to the chassis 24 may be provided in either one of thechassis opposing face and the hub opposing face. Since the gas dynamicpressure generating groove is provided in an area outwardly in theradial direction with respect to the inner periphery of the magnet 28,the gaseous body present in this area can be efficiently pushed towardthe interior.

A dynamic pressure generating groove that pushes the gaseous bodypresent in the first gap 202 toward the magnet 28 when the hub 26rotates may be provided in either one of the opposing faces in theradial direction forming the first gap 202. A dynamic pressuregenerating groove that pushes the gaseous body present in the second gap204 toward the first gap 202 when the hub 26 rotates may be provided ineither one of the opposing faces in the axial direction forming thesecond gap 204. A dynamic pressure generating groove that pushes thegaseous body present in the third gap 206 toward the second gap 204 whenthe hub 26 rotates may be provided in either one of the opposing facesin the radial direction forming the third gap 206.

Such a gas dynamic pressure generating groove may be provided in solo orin a multiple manner. The gas dynamic pressure generating groove isformed in, for example, a spiral shape or in a herringbone shape.

In this embodiment, as an example, a dynamic pressure generating groove210 that is in a spiral shape or the like is formed in an area which isthe lower end face of the mount part 26J of the hub 26 and which faceswith the upper face of the recess 24N of the chassis 24 in the axialdirection. In this case, it becomes possible for the disk drive device 1to prevent the gasified lubricant 20 from diffusing around the magneticrecording disks 62.

The dynamic pressure generating groove 210 can be provided through, forexample, a technique of directly forming such a groove in the lower endof the mount part 26J or through a technique of fastening an additionalmember formed with the dynamic pressure generating groove 210 in advanceto the lower end of the mount part 26J. This additional member can beformed through, for example, a technique of pressing a metal material orthe like, or a technique of molding and shaping a resin material. Thedynamic pressure generating groove 210 can be also formed throughtechniques, such as pressing, ball-rolling, electro-chemical machining,or cutting. The same is true of the respective opposing faces formingthe second gap 204 and the third gap 206 which may be provided with agas dynamic pressure generating groove.

The stator core 32 includes an annular part, and, for example, 12salient poles protruding outwardly in the radial direction from theannular part. The stator core 32 has the inner periphery of the annularpart joined with the protrusion 24E by press-fitting, bonding or acombination thereof. The stator core 32 is formed by laminating andcaulking, for example, five to 20 magnetic steel sheets together eachhaving a thickness of 0.2 to 0.35 mm. In this embodiment, as an example,12 magnetic steel sheets each having a thickness of 0.2 mm are laminatedtogether. A surface layer is provided on the surface of the stator core32. An insulation painting, such as electro-deposition coating or powdercoating, is applied to the surface of the stator core 32, i.e., thesurface layer.

The coils 30 are each formed by winding a conductor wire around eachsalient pole of the stator core 32 by a predetermined number of turns.The coil 30 generates a field magnetic field along the salient pole whena drive current is caused to flow through the coil 30. The conductorwire is formed by, for example, covering the surface of a wire core likesoft copper with an insulation layer like a urethane resin. Alubrication material is applied to the surface of the conductor wire toreduce a frictional resistance. The lubrication material is not limitedto any particular one, but in this embodiment, a lubrication materialcontaining a polyamide compound as a primary constituent is applied tothe wire to reduce an adhesion of hydrocarbon like paraffin as little aspossible. In addition, the coil 30 wound around the salient pole isdipped in pure water or a cleaning liquid containing surfactant agent oran ester and is cleaned while being irradiated with ultrasound tofurther reduce hydrocarbon sticking to the surface of the conductorwire. As a result, the total amount of hydrocarbons sticking to the coil30 becomes smaller than the total amount of polyamide compounds stickingto the coil 30.

The hub 26 includes a sleeve encircling part 26A fastened to the sleeve42 in a manner encircling the sleeve 42, and facing with the flangeencircling part 18, an extended part 26B that extends from the sleeveencircling part 26A toward the flange 16 and enters the interior of theflange encircling part 18, a disk part 26D that extends outwardly in theradial direction from the center of the hub 26, an annular part 26E thatprojects from the outer periphery of the disk part 26D downwardly in theaxial direction, and the mount part 26J that extends outwardly in theradial direction from the lower outer periphery of the annular part 26E.

The sleeve encircling part 26A faces with the protrusion 24E with a gapin the radial direction, and faces with the flange encircling part 18with a gap in the axial direction. In addition, the extended part 26Bfaces with the flange encircling part 18 with a gap in the radialdirection, and faces with the flange 16 with a gap in the axialdirection.

The disk part 26D, the annular part 26E, and the mount part 26J areformed in an annular shape coaxially with each other along the rotationaxis R. As a result, the hub 26 is in a substantially cup shape. Thedisk part 26D, the annular part 26E, and the mount part 26J are formedtogether as a single piece. The hub 26 is formed of a ferrous materialwith a soft magnetism like SUS 430F. The annular part 26E of the hub 26is to be engaged with the center hole of the magnetic recording disk 62in a disk shape, and such a magnetic recording disk 62 is to be mountedon the mount part 26J. The mount part 26J has at least a part thatenters the recess 24N provided in the bottom plate 24A of the chassis24. Gaps between the recess 24N, the mount part 26J, and the opposingwall 24F form a labyrinth.

In order to let the four magnetic recording disks 62 spaced apart fromeach other, the spacers 72 are provided. The spacers 72 are each in ahollow ring shape, and each have an inner periphery engaged with theannular part 26E. Each spacer 72 is held between the lower magneticrecording disk 62 and the upper magnetic recording disk 62. In addition,in order to prevent the uppermost magnetic recording disk 62 from beingdetached from the hub 26, the clamper 78 is provided. The clamper 78 isin a hollow disk shape, and is fastened to the upper face of the hub 26by, for example, an unillustrated fastener like a screw. Accordingly,the clamper 78 holds the uppermost magnetic recording disk 62 to preventit from being detached from the hub 26.

The magnet 28 is in a hollow ring shape, and has an outer peripheryfastened to the inner periphery of the hub 26 by, for example, bonding.The upper face of the magnet 28 abuts a protrusion projecting from theinternal face of the hub 26. The magnet 28 is formed of, for example, aferrite-based magnetic material or a rare-earth-based magnetic material.As a binder, a resin like polyamide is contained in the magnet 28. Themagnet 28 may be formed by laminating a ferrite-based magnetic layer anda rare-earth-based magnetic layer. The magnet 28 has a surface layerformed by, for example, electro-deposition coating or a spray painting.The surface layer suppresses an oxidization of the magnet 28, orsuppresses a peeling of the surface of the magnet 28. The magnet 28 has,for example, 16 polarities in the inner periphery in the circumferentialdirection, and has the inner periphery facing with the outer peripheryof each salient pole of the core 32 with a gap in the radial direction.The height dimension of the magnet 28, i.e., the thickness thereof is100 to 200% of the thickness of the stator core 32. In this embodiment,the thickness of the magnet 28 is substantially 180% of the thickness ofthe stator core 32.

Next, an explanation will be given of the fluid bearing unit and theproximal area thereof with reference to FIG. 3. FIG. 3 is an enlargedcross-sectional view illustrating the proximal area of the shaft body 6and that of the bearing body 8 in FIG. 2 in an enlarged manner. FIG. 3mainly illustrates the left part relative to the rotation axis R.

The fluid bearing unit includes a gas-liquid interface between thelubricant 20 and the atmosphere gaseous body in the gap between theshaft body 6 and the bearing body 8. In this embodiment, a firstgas-liquid interface 124 to be discussed later and that is thegas-liquid interface at the chassis side is exposed in the area heldbetween the chassis 24 and the hub 26. In addition, this fluid bearingunit has a second gas-liquid interface 122 to be discussed later andthat is a gas-liquid interface at the hub side, and is exposed in thearea opened at a distant side of the hub 26 from the chassis 24 in theaxial direction.

First, a structure of the shaft body 6 will be explained in detail. Theshaft holder 112 of the shaft body 6 includes, as explained above, theflange 16 and the flange encircling part 18. The flange 16 has a shaftinsertion hole 16B formed at the center in a coaxial manner with therotation axis R. The flange encircling part 18 protrudes from the outerperiphery of the flange 16 toward the hub 26. The shaft holder 112 has,for example, the flange 16 and the flange encircling part 18 formedtogether as a single piece. In this case, the manufacturing error of theshaft holder 112 can be reduced, and a joining work can be eliminated.Alternatively, a deformation of the shaft holder 112 due to an impactload can be suppressed. The shaft holder 112 is formed by, for example,cutting and machining a metal material like SUS 303. Depending on theapplication of the disk drive device 100 and the limitation in thedesigning thereof, the shaft holder 112 may be formed of other materialslike a resin, and may be formed through other techniques, such aspressing and molding.

The shaft holder 112 has the flange encircling part 18 engaged with theopening 24D of the chassis 24, and has the outer periphery of the flangeencircling part 18 bonded with the inner periphery of the opening 24Dby, for example, a bond 76, thereby being fastened to the chassis 24.The flange encircling part 18 has an upper end 18C located at an areawhere a second radial dynamic pressure generating groove 50 to bediscussed later is provided in the axial direction or locatedthereabove, and faces with the sleeve encircling part 26A of the hub 26with a gap.

The shaft 110 has the shaft flange 12 provided at the one-end side asexplained above. The shaft flange 12 is disposed so as to cover theupper face of the sleeve 42 in the axial direction with a gap, and toface the sleeve encircling part 26A of the hub 26 in the radialdirection with a gap. The shaft flange 12 has, in its outer periphery, atapered face 12J having a distance from the rotation axis R in theradial direction becoming large as becoming close to the chassis 24. Inaddition, the shaft flange 12 is formed with a groove 12A in the innerperiphery and in an annular shape as viewed from the top. A part of thecap 48 to be discussed later enters this groove 12A with a gap.

The shaft 110 has a retainer hole 10A that is formed in one end, i.e.,the end at a side where the shaft flange 12 is formed and retains thefastener like the screw 74. The shaft 110 has another end inserted in ashaft insertion hole 16B of the flange 16, and is fastened thereto by,for example, interference fitting. This interference fitting can berealized by, for example, pressing the shaft 110 in the shaft insertionhole 16B, thermal insertion, inserting the shaft 110 cooled by a liquidnitrogen beforehand into the shaft insertion hole 16B and letting such acold shaft 110 to be a normal temperature. Bonding may be applied insuch an interference fitting.

The shaft 110 and the shaft flange 12 are formed integrally. In thiscase, the manufacturing error between the shaft 110 and the shaft flange12 can be reduced, and a joining work can be eliminated. Depending onthe application and a limitation in the designing, the shaft flange 12and the shaft 110 may be formed separately.

The shaft 110 is formed by, for example, cutting and machining orgrinding and machining a ferrous material, such as SUS 420 J2, SUS 430,or SUS 303. The shaft 110 may be quenched in order to enhance thehardness. The shaft 110 may have an outer periphery 10C and a lower face12C of the shaft flange 12 polished in order to enhance the dimensionalprecision. The shaft 110 may be formed of other materials like a resinand may be formed through other techniques, such as pressing andmolding.

Next, a structure of the bearing body 8 will be explained in detail. Thebearing body 8 includes the sleeve 42 in a substantially cylindricalshape and encircling a middle part of the shaft 110, i.e., a partbetween the shaft flange 12 and the flange 16. The sleeve 42 is joinedwith the sleeve encircling part 26A of the hub 26. The sleeve 42 has anupper end facing with the lower face 12C of the shaft flange 12 with agap in the axial direction, and has a lower end facing with an upperface 16A of the flange 16 with a gap in the axial direction. Accordingto such a structure, the sleeve 42 is freely rotatable with respect tothe shaft 110, and thus the hub 26 joined with the sleeve 42 is freelyrotatable with respect to the chassis 24.

The bearing body 8 is formed by, for example, cutting and machining ametal material, such as SUS 430 or stainless steel. The bearing body 8may have a surface layer formed by, for example, electroless nickelplating. The bearing body 8 may be formed of other materials like brass.

The sleeve 42 is in a substantially cylindrical shape with a hollow, andincludes an inner periphery 42A, an outer periphery 42B, an upper face42C, and a lower face 42D. The sleeve 42 has the inner periphery 42Aencircling the shaft 110 with a gap.

Provided in a gap in the radial direction between the inner periphery42A of the sleeve 42 and the outer periphery 10C of the shaft 110 are,from top to bottom in this order, a first radial dynamic pressurebearing 80, an intermediate space 82, and a second radial dynamicpressure bearing 84 in this order. The first radial dynamic pressurebearing 80 is provided above the second radial dynamic pressure bearing84 so as to be distant therefrom, and the intermediate space 82 isprovided between the first radial dynamic pressure bearing 80 and thesecond radial dynamic pressure bearing 84. A first radial dynamicpressure generating groove 52 to generate radial dynamic pressure isprovided in an area corresponding to the first radial dynamic pressurebearing 80 in the inner periphery 42A of the sleeve 42. The first radialdynamic pressure generating groove 52 may be provided in the outerperiphery 10C of the shaft 110 instead of the sleeve 42. A second radialdynamic pressure generating groove 50 to generate radial dynamicpressure is provided in an area corresponding to the second radialdynamic pressure bearing 84 in the inner periphery 42A of the sleeve 42.The second radial dynamic pressure generating groove 50 may be providedin the outer periphery 10C of the shaft 110 instead of the sleeve 42. Alarge-diameter part recessed outwardly in the radial direction isprovided in an area corresponding to the intermediate space 82 of theinner periphery 42A of the sleeve 42.

Still further, the sleeve 42 has a communication channel BP which isprovided in the outer periphery 42B and which runs in the axialdirection so as to be in communication with a first thrust opposing part86 and a second thrust opposing part 88 to be discussed later. Thecommunication channel BP is formed in the outer periphery 42B of thesleeve 42 so as to include grooves running from the upper end to thelower end in the axial direction.

FIG. 4 is a pressure distribution diagram exemplarily illustrating adistribution DP of radial dynamic pressures of the disk drive device 100according to this embodiment. An arrow H indicates a direction in whichpressure is high. The first radial dynamic pressure generating groove 52may be formed in, for example, a herringbone shape with a bent part. Anapex B1 of the bent part of the first radial dynamic pressure generatinggroove 52 is located above an axial-direction center C1 of the areawhere the first radial dynamic pressure generating groove 52 isdisposed. In this case, the pressure distribution DP becomes thesmallest at the lower end of the first radial dynamic pressuregenerating groove 52, becomes higher toward the apex B1 of the bentpart, becomes the maximum near the apex B1 of the bent part, and becomessmaller toward the upper side from the apex B1 of the bent part. Thatis, a maximum-pressure generating part P1 of the dynamic pressuregenerated by the first radial dynamic pressure groove 52 in the axialdirection is produced near the apex B1 of the bent part. In other words,the maximum-pressure generating part P1 of the first radial dynamicpressure generating groove 52 is located at the upper-flange-12 siderelative to the axial-direction center C1. According to such astructure, when the bearing body 8 and the shaft body 6 relativelyrotate, the first radial dynamic pressure bearing 80 pushes thelubricant 20 toward a first thrust opposing part 86 to be discussedlater. The first radial dynamic pressure generating groove 52 may beformed in other shapes like a spiral shape.

Conversely, the second radial dynamic pressure generating groove 50 maybe formed in, for example, a herringbone shape with a bent part. An apexB2 of the bent part of the second radial dynamic pressure generatinggroove 50 is located below an axial-direction center C2 of the areawhere the second radial dynamic pressure generating groove 50 isdisposed. Because of the similar mechanism to that of theabove-explained maximum-pressure generating part P1, a maximum-pressuregenerating part P2 of the second radial dynamic pressure generatinggroove 52 is located at the lower-flange-16 side relative to theaxial-direction center C2. According to such a structure, when thebearing body 8 and the shaft body 6 relatively rotate, the second radialdynamic pressure bearing 84 pushes the lubricant 20 toward a secondthrust opposing part 88 to be discussed later. Like the first radialdynamic pressure generating groove 52, the second radial dynamicpressure generating groove 50 may be formed in other shapes like aspiral shape.

The groove width of the first radial dynamic pressure generating groove52 becomes narrower at the center (the apex B1 of the bent part) thanthe ends of the area where such a dynamic pressure generating groove isdisposed, and the groove depth of the first radial dynamic pressuregenerating groove 52 becomes shallower at the center (the apex B1 of thebent part) than the ends of the area where such a dynamic pressuregenerating groove is disposed. The first radial dynamic pressuregenerating groove 52 may have at least one of the groove width and thegroove depth substantially uniform.

Likewise, the groove width of the second radial dynamic pressuregenerating groove 50 becomes narrower at the center (the apex B2 of thebent part) than the ends of the area where such a dynamic pressuregenerating groove is disposed, and the groove depth of the second radialdynamic pressure generating groove 50 becomes shallower at the center(the apex B2 of the bent part) than the ends of the area where such adynamic pressure generating groove is disposed. The second radialdynamic pressure generating groove 50 may have at least one of thegroove width and the groove depth substantially uniform.

Returning to FIG. 3, the first thrust opposing part 86 is provided in agap between the shaft flange 12 and the sleeve 42 where the lower face12C and the upper face 42C face with each other in the axial direction.A first thrust dynamic pressure generating groove 54 to generate thrustdynamic pressure is provided in an area of the upper face 42C of thesleeve 42 corresponding to the first thrust opposing part 86. The firstthrust dynamic pressure generating groove 54 may be provided in an areaof the lower face 12C of the shaft flange 12 corresponding to the firstthrust opposing part 86 instead of the sleeve 42. Conversely, a secondthrust opposing part 88 is provided in a gap between the flange 16 andthe sleeve 42 where the upper face 16A and the lower face 42D face witheach other in the axial direction. A second thrust dynamic pressuregenerating groove 56 to generate thrust dynamic pressure is provided inan area of the lower face 42D of the sleeve 42 corresponding to thesecond thrust opposing part 88. The second thrust dynamic pressuregenerating groove 56 may be provided in an area of the upper face 16A ofthe flange 16 corresponding to the second thrust opposing part 88instead of the sleeve 42.

The first thrust dynamic pressure generating groove 54 and the secondthrust dynamic pressure generating groove 56 are each formed in, forexample, a spiral shape. The first thrust dynamic pressure generatinggroove 54 and the second thrust dynamic pressure generating groove 56may be formed in other shapes like a herringbone shape. The secondradial dynamic pressure generating groove 50, the first radial dynamicpressure generating groove 52, the first thrust dynamic pressuregenerating groove 54, and the second thrust dynamic pressure generatinggroove 56 are formed by, for example, pressing, ball-rolling,electro-chemical machining, and cutting. Those dynamic pressuregenerating grooves may be formed through different techniques,respectively.

The outer periphery of the extended part 26B has an inclined face 26BAprovided in an area where it faces an inner periphery 18A of the flangeencircling part 18 in the radial direction and having an outer diameterbecoming small as becoming close to the upper end of the extended part26B. A gap between the inclined face 26BA and the inner periphery 18A inthe radial direction includes a tapered space gradually becoming widertoward the upper space in the axial direction. The inclined face 26BAand the inner periphery 18A contact a second gas-liquid interface 122 ofthe lubricant 20 to be discussed later, and form a second capillary seal92 that suppresses a spill of the lubricant 20 by capillary force. Forexample, the second gas-liquid interface 122 is located at the disposedarea of the second radial dynamic pressure generating groove 50 orthereabove in the axial direction. For example, the second gas-liquidinterface 122 is provided outwardly in the radial direction with respectto the first thrust opposing part 86 and the second thrust opposing part88.

The sleeve encircling part 26A faces the shaft flange 12 with a gap inthe radial direction at the upper side of the sleeve 42. A gap in theradial direction between an inner periphery 26AA of the sleeveencircling part 26A and the tapered face 12J of the shaft flange 12forms a tapered space gradually becoming wide toward the upper space.The inner periphery 26AA and the tapered face 12J contact a firstgas-liquid interface 124 of the lubricant 20, and form a first capillaryseal 90 that suppresses a spill of the lubricant 20 by capillary force.

The cap 48 is a hollow ring thin in the axial direction, and is formedby, for example, cutting and machining a stainless steel material, suchas SUS 303 or SUS 430. The cap 48 may be formed of other metal or resinmaterials and may be formed by pressing or molding. The cap 48 isfastened to the bearing body 8 so as to have an inner peripheryencircling the shaft body 6 with a gap. More specifically, the innerperiphery of the cap 48 faces the outer periphery of the upper end ofthe shaft 110 in a non-contact manner, and the outer periphery of thecap 48 is bonded and fastened to the upper end face of the sleeveencircling part 26A. The cap 48 covers the first gas-liquid interface124 and a part of the shaft flange 12. The inner periphery of the cap 48is provided with a circular projection 48E that extends downwardlyaround the rotation axis R. Apart of the circular projection 48E entersthe circular groove 12A in the axial direction provided around therotation axis R in the upper face of the shaft flange 12. Note that thecap 48 may be fastened to the shaft body 6 and may be provided in anon-contact manner with the hub 26.

Next, an explanation will be given of the lubricant. Various materials,such as a synthetic oil, a mineral oil, and an ionic liquid, areapplicable as the lubricant. In this embodiment, as an example, thelubricant 20 adopted contains a base oil that is a synthetic oilcontaining primary of an ester-based compound.

The lubricant 20 is continuously present in a gap between the bearingbody 8 and the shaft body 6 from the first gas-liquid interface 124 tothe second gas-liquid interface 122. More specifically, the lubricant 20is present in areas including a gap between the tapered face 12J and theinner periphery 26AA, a gap between the shaft flange 12 and the sleeve42, a gap in the radial direction between the sleeve 42 and the shaft110, a gap between the sleeve 42 and the flange 16, a gap between theextended part 26B and the flange 16, and a gap between the inclined face26BA and the inner periphery 18A. In other words, the lubricant 20 iscontinuously filled between the first gas-liquid interface 124 and thesecond gas-liquid interface 122, i.e., areas including the first thrustopposing part 86, the first radial dynamic pressure bearing 80, theintermediate space 82, the second radial bearing 84, and the secondthrust opposing part 88. In addition, the lubricant 20 is alsocontinuously filled in an area including the communication channel BPfrom the first gas-liquid interface 124 to the second gas-liquidinterface 122.

The lubricant 20 of this embodiment is fluorescent. The termfluorescence in the explanation for this embodiment means fluorescencein the broad sense including phosphorescence in addition to fluorescencein the narrow sense. For example, the base oil itself may contain afluorescent material with a fluorescence characteristic. According tothe lubricant 20 of this embodiment, a fluorescence substance is addedto the base oil. The fluorescence substance is not limited to anyparticular one, but various fluorescence substances, such as inorganicsubstances including a rare-earth salt, a uranyl salt, a platinum cyancomplex salt, and a tungsten acid salt, and organic substances includingbenzene, aniline, anthracene, a phthalein-based pigment, aporphyrin-based pigment, and a cyan-based pigment, are applicable.According to the lubricant 20 of this embodiment, as an example,fluorescein as a fluorescence substance is added. Fluorescein emitsvisible light that is green spectrum when irradiated with ultravioletrays with a shorter wavelength than that of visible light. This may becaused by a photoluminescence phenomenon.

When a fluorescence substance is added to the lubricant, such afluorescence substance may chemically react with the base oil of thelubricant, which deteriorates the base oil. Hence, it is desirable thatthe fluorescence substance should deteriorate the base oil as little aspossible even if added to the base oil. In addition, when the lubricantis used at a temperature equal to or higher than the boiling point ofthe fluorescence substance, the fluorescence substance is easilyvaporized, and may stick to the surface of the magnetic recording disk,which causes a breakdown. Hence, the boiling point of the fluorescencesubstance contained in the lubricant 20 of this embodiment is set to behigher than the boiling point of water. In this case, when the lubricantis used within a temperature range that is equal to or lower than theboiling point of water, the vaporization of the fluorescence substancecan be suppressed. In other words, when the use temperature is near theboiling point of water, if the use temperature is equal to or lower thanthe boiling point of water, the disk drive device 100 can be used.

The containing rate of the fluorescence substance in the lubricant canbe set to, for example, equal to or greater than 0.001 mass %. In thiscase, the lubricant emits fluorescence when irradiated with light havinga predetermined characteristic. In this embodiment, as an example, thecontaining rate of the fluorescence substance in the lubricant 20 is setto equal to or greater than 0.01 mass %. In this case, when thelubricant 20 is irradiated with predetermined light, the lubricant 20emits further intensive fluorescence in comparison with a case in whichthe containing rate is 0.001 mass %. When, however, the containing rateof the fluorescence substance in the lubricant increases, the costs ofthe lubricant may increase. In this embodiment, as an example, thecontaining rate of the fluorescence substance in the lubricant 20 is setto equal to or smaller than 1 mass %. In this case, it is confirmed thatthe increase in the costs of the lubricant 20 is within a practicalrange.

With respect to the lubricant 20, an explanation will be below given ofa labyrinth structure. As explained above, the sleeve encircling part26A faces with the protrusion 24E with a gap in the radial direction,and faces with the upper end 18C of the flange encircling part 18 with agap in the axial direction. Hence, the respective gaps between thesleeve encircling part 26A, the protrusion 24E, and the upper end 18Cform a first labyrinth. In addition, the lower end of the mount part 26Jof the hub 26 enters the recess 24N of the chassis 24, and forms asecond labyrinth that includes the fourth gap 208, the first gap 202,the second gap 204, and the third gap 206. Still further, the gapbetween the cap 48 and the shaft flange 12 forms a third labyrinth.

Next, an explanation will be given of an operation of the fluid bearingunit. When the bearing body 8 rotates relative to the shaft body 6, thesecond radial dynamic pressure generating groove 50, the first radialdynamic pressure generating groove 52, the first thrust dynamic pressuregenerating groove 54, and the second thrust dynamic pressure generatinggroove 56 respectively generate dynamic pressures to the lubricant 20.Such dynamic pressures support the rotating body 4 coupled with thebearing body 8 in a non-contact manner with respect to the stationarybody 2 coupled with the shaft body 6.

Next, an explanation will be given of an example method formanufacturing the disk drive device 100 of this embodiment.

First, the sleeve 42 is fastened to the hub 26 by, for example, bonding.Next, the sleeve 42 is held between the shaft holder 112 and the shaft110, and the shaft holder 112 and the shaft 110 are joined with eachother by a technique that is a combination of press-fitting and bonding.In the following explanation, the assembled piece including the hub 26,the sleeve 42, the shaft holder 112, and the shaft 110 is referred to asa subassembly. Subsequently, the lubricant 20 is filled in a region ofthe sub as sembly where the lubricant should be filled. For example, thesub assembly is left in a pressure-reduced atmosphere to draw air in theregion where the lubricant should be filled. Next, the lubricant 20 isapplied to, for example, the gap between the hub 26 and the shaft flange12. Subsequently, the atmosphere is returned to an atmospheric pressure,and the lubricant 20 is filled in the region of the sub assembly wherethe lubricant should be filled, thereby finishing the bearing unit.

Next, with respect to the bearing unit filled with the lubricant 20, thefirst gas-liquid interface 124 of the lubricant 20 is observed toconfirm that the first gas-liquid interface 124 is located within apredetermined range. At this time, if the lubricant is substantiallytransparent, it takes a time for checking. In this embodiment, since thelubricant 20 is fluorescent, when, for example, input light likeultraviolet rays is emitted, output light with a predeterminedwavelength is output. FIG. 6 is a cross-sectional view illustrating astep for emitting input light to the lubricant 20 and for obtainingoutput light. FIG. 6 corresponds to FIG. 2. In this step, input lightthat is ultraviolet rays with a predetermined wavelength is emitted tothe first gas-liquid interface 124 in the gap between the hub 26 of thebearing unit and the shaft flange 12 thereof, and output light like blueor green fluorescence is obtained. In this case, it becomes easy tocheck the first gas-liquid interface 124, and necessary time forchecking can be reduced, and thus the productivity is improved. In thiscase, moreover, output light with a predetermined wavelength isobtainable, and thus the location of the first gas-liquid interface 124can be inspected by calculating the light intensity of the output lightwith the predetermined wavelength. In this case, the checking of thefirst gas-liquid interface 124 can be further facilitated.

Subsequently, the cap 48 and the magnet 28 are respectively fastened tothe hub 26 by bonding. Next, the chassis 24 having the stator core 32with coils 30 fastened is prepared, and the bearing unit is fastened tothe chassis 24 by bonding. Subsequently, the magnetic recording disks62, the clamper 78, and the spacers 72 are attached. Next, the datareader/writer 60 and the top cover 22 are attached. Subsequently, thedisk drive device 100 is finished through predetermined steps like aninspection. Note that the above-explained steps are merely examples, andthe disk drive device 100 is maunfacturable through different steps.

Next, an explanation will be given of an operation of the disk drivedevice 100 structured as explained above. In order to rotate themagnetic recording disks 62, a drive current of three phases is suppliedto the coils 30. When the drive current flows through the respectivecoils 30, field magnetic fluxes are produced along the salient poles ofthe stator core 32. A mutual effect of such field magnetic fluxes andthe magnetic fluxes of the drive magnetic poles of the magnet 28 appliestorque to the magnet 28, and thus the hub 26 and the magnetic recordingdisk 62 s engaged therewith start rotating. While at the same time, thevoice coil motor 66 swings the swing arm 64, and thus therecording/playing head comes and goes within the swingable range overthe magnetic recording disk 62. The recording/playing head convertsmagnetic data recorded in the magnetic recording disk 62 into electricsignals, and transmits the electric signals to an unillustrated controlboard, and writes data transmitted from the control board in the form ofelectric signals on the magnetic recording disk 62 as magnetic data.

The disk drive device 100 according to this embodiment employing theabove-explained structure accomplishes the following advantages. Whenthe bearing body 8 and the shaft body 6 relatively rotate, a pressuredifference may be generated in the lubricant present between the firstradial dynamic pressure bearing 80 and the second radial dynamicpressure bearing 84. This pressure difference causes the lubricant 20 tobe easily leaked out from the first capillary seal 90 and the secondcapillary seal 92. According to this embodiment, however, since thecommunication channel BP is provided which causes the first thrustopposing part 86 and the second thrust opposing part 88 to be incommunication with each other, the pressure difference between the firstcapillary seal 90 and the second capillary seal 92 becomes small. Hence,it becomes possible for the disk drive device 100 to prevent thelubricant 20 from leaking out.

According to the disk drive device 100, when the bearing body 8 and theshaft body 6 relatively rotate, the first radial dynamic pressurebearing 80 pushes the lubricant 20 toward the first thrust opposing part86. Hence, a reduction of the dynamic pressure can be suppressed nearthe boundary between the first thrust opposing part 86 and the firstradial dynamic pressure bearing 80. In addition, the second radialdynamic pressure bearing 84 pushes the lubricant 20 toward the secondthrust opposing part 88, and thus a reduction of the dynamic pressurecan be suppressed near the boundary between the second thrust opposingpart 88 and the second radial dynamic pressure bearing 84. As a result,the possibility that the rotating body 4 contacts the stationary body 2can be reduced.

According to the disk drive device 100, the maximum-pressure generatingpart P1 of the dynamic pressure generated by the first radial dynamicpressure generating groove 52 in the axial direction is located at theshaft-flange-12 side relative to the axial-direction center C1 of thearea where the first radial dynamic pressure generating groove 52 isdisposed. Therefore, an effective bearing span can be elongated upwardlyin the axial direction. In addition, the maximum-pressure generatingpart P2 of the dynamic pressure generated by the second radial dynamicpressure generating groove 50 in the axial direction is located at theflange-16 side relative to the axial-direction center C2 of the areawhere the second radial dynamic pressure generating groove 50 isdisposed, and thus the effective bearing span can be elongateddownwardly in the axial direction.

According to the disk drive device 100, the first radial dynamicpressure generating groove 52 has the apex B1 of the bent part locatedat the upper-flange-12 side relative to the axial-direction center C1 ofthe area where such a radial dynamic pressure generating groove isdisposed. Hence, the effective bearing span can be further elongatedupwardly in the axial direction. In addition, the second radial dynamicpressure generating groove 50 has the apex B2 of the bent part locatedat the lower-flange-16 side relative to the axial-direction center C2 ofthe area where such a radial dynamic pressure generating groove isdisposed, and thus the effective bearing span can be further elongateddownwardly in the axial direction.

According to the disk drive device 100, the shaft flange 12 has aportion formed integrally with the shaft 110, and thus the possibilitythat the shaft flange 12 is detached from the shaft 110 can be reduced,while at the same time, a reduction of the joining strength between theshaft flange 12 and the shaft 110 when the disk drive device 100 is inuse can be suppressed.

According to the disk drive device 100, the flange encircling part 18has the upper end 18C located at the area where the second radialdynamic pressure generating groove 50 is disposed or thereabove in theaxial direction, and thus a volume of the gap between the innerperiphery 18A of the flange encircling part 18 and the inclined face26BA of the extended part 26B can be increased. In addition, the secondgas-liquid interface 122 is located at the area where the second radialdynamic pressure generating groove 50 is disposed or thereabove in theaxial direction, and thus the second gas-liquid interface 122 can retaina large amount of lubricant 20, reducing the possibility of the failuredue to the lack of lubricant 20.

When currents flow through the coils, and a temperature rises due to theJoule heat, paraffin components like hydro carbon sticking to thesurfaces of the coils are volatilized and diffused in surrounding areas,and eventually, reach the surfaces of the magnetic recording disks. Thevolatilized components build up condensation and are gradually depositedon the surfaces of the magnetic recording disks, disturbing theoperation of a disk drive device. In the worst case, this causes thebreakdown of the disk drive device. According to the disk drive device100, however, the total amount of hydro carbon sticking to the coils 30is less than the total amount of polyamide compounds sticking to thecoils 30. Hence, a possibility that a failure due to the volatilizationof hydro carbon occurs can be reduced.

According to the disk drive device 100, the sleeve encircling part 26A,the protrusion 24E, and the upper end 18C of the flange encircling part18 form the first labyrinth. This first labyrinth suppresses a spillingand vaporization of the lubricant 20 from the second gas-liquidinterface. In addition, the lower end of the mount part 26J of the hub26 enters the recess 24N of the chassis 24, and forms the secondlabyrinth. This second labyrinth prevents, even if the vaporizedlubricant 20 reaches the interior of the hub 26, i.e., the region wherethe coils 30 and the stator core 32 are disposed beyond the firstlabyrinth, the vaporized lubricant 20 from further reaching the exteriorof the hub 26, i.e., the disposed area of the magnetic recording disks62 (the clean space 70) through the recess 24N due to a passageresistance.

Still further, the gap between the cap 48 and the groove 12A of theshaft flange 12 forms the third labyrinth. This third labyrinth preventsthe lubricant 20 from spilling and vaporizing from the first gas-liquidinterface 124. Hence, the disk drive device 100 can prevent thevaporized lubricant 20 from building up condensations on the surface ofthe magnetic recording disks 62 and being deposited thereon. Thisenables a further increase in the recording capacity.

Since the first to third labyrinths suppress a vaporization, etc., ofthe lubricant 20, a time until the disk drive device 100 lacks thelubricant 20 can be elongated. This extends the operation life of thedisk drive device 100.

According to the disk drive device 100, the lower end face of the mountpart 26J of the hub 26 which forms the second gap 204 is provided withthe gas dynamic pressure generating groove 210. Hence, the gas presentin the second gap 204 is pushed to the interior of the hub 26 when thehub 26 rotates, and it becomes possible for the disk drive device 100 toprevent the vaporized lubricant 20 from reaching the clean space 70.

MODIFIED EXAMPLE

Next, an explanation will be given of a structure in which the shaftholder 112 is provided with an outward protrusion, while the opening 24Dof the chassis 24 is provided with an inward recess corresponding to theoutward protrusion. FIG. 5 is a cross-sectional view illustrating a diskdrive device 200 according to a modified example, and illustrating theproximal area of an inward recess 224G. The disk drive device 200 has anoutward protrusion 218G provided on a shaft holder 212, and has theinward recess 224G provided in an opening 224D of a chassis 224 andcorresponding to the outward protrusion 218G. According to this modifiedexample, the shaft holder 212 corresponds to the shaft holder 112 of theabove-explained embodiment, and the chassis 224 corresponds to thechassis 24 of the above-explained embodiment. The shapes of only theshaft holder 212 and the chassis 224 differ from those of theabove-explained embodiment. In this modified example, the outwardprotrusion 218G is provided around the outer periphery of a flangeencircling part 218 at the one-end side like an outward flange with alarger diameter than the opening 224D. The inward recess 224G isprovided in the opening 224D of the chassis 224 at the one open end sidein a concaved shape retaining therein the outward protrusion 218G. Whenthe inward recess 224G is caused to abut against the outward protrusion218G, the precision of the engagement of the chassis 224 with the shaftholder 212 can be improved. In addition, when the disk drive device 200receives shock, the outward protrusion 218G serves as a stopper, andthus the possibility that the shaft holder 212 is detached from thechassis 224 can be reduced.

When the similar structure is applied to the shaft 110 and the flange16, the same advantage can be accomplished.

The structure of the disk drive device according to the embodiment andthe operation thereof, and, the structure of the disk drive device ofthe modified example and the operation thereof were explained above.Those are merely examples, and a combination of the respectivestructural components permits various options, and such a structure isalso within the scope and spirit of the present invention.

In the above-explained embodiment and the modified example, theexplanation was given of the example case in which the rotating body 4is coupled with the bearing body 8, and the shaft body 6 is coupled withthe stationary body 2, but the present invention is not limited to thiscase. A structure may be employed in which the rotating body 4 iscoupled with the shaft body 6, and the bearing body 8 is coupled withthe stationary body 2.

In the above-explained embodiment and the modified example, although theexplanation was given of the example case in which the stator core isencircled by the magnet, the present invention is not limited to thiscase. For example, a structure may be employed in which the magnet isencircled by the stator core.

In the above-explained embodiment and the modified example, theexplanation was given of the example case in which the first thrustdynamic pressure generating groove 54 is provided in an area of theupper face 42C of the sleeve 42 corresponding to the first thrustopposing part 86, but the present invention is not limited to this case.For example, a structure may be employed in which no thrust dynamicpressure generating groove is provided at all in the upper face 42C andthe lower face 12C of the shaft flange 12 in the first thrust opposingpart 86.

In the above-explained embodiment, the explanation was given of theexample case in which the lubricant 20 that contains the ester-basedcompound as the primary element was used, but the present invention isnot limited to this case. For example, a lubricant containing an ionicliquid may be utilized. When the lubricant contains the ionic liquid, avaporization of the lubricant can be suppressed, and thus the amount oflubricant diffused in the disk drive device can be reduced. This reducesthe amount of the lubricant deposited on the magnetic recording disk.The ionic liquid is not limited to any particular one, but an ionicliquid disclosed in JP 2007-120653 A is applicable. The disclosure ofthis patent application is incorporated in this specification byreference.

What is claimed is:
 1. A disk drive device comprising: a chassis; anannular rotator having an outer periphery that is engagable with arecording disk, and having an inner periphery fastened with an annularmagnet; a fluid bearing unit that supports the rotator in a mannerfreely rotatable relative to the chassis; an opposing wall that isformed annularly on a surface of the chassis at the rotator side, andfaces with at least partially the inner periphery of the rotator in aradial direction; a first gap running in an axial direction between theinner periphery of the rotator and the opposing wall; and a second gapcontinuous from the first gap, and running in the radial directionbetween an end face of the rotator and the chassis, wherein: the fluidbearing unit comprises a shaft body, a bearing body, and a dynamicpressure generating groove; the shaft body comprises a shaft; thebearing body comprises a sleeve that encircles the shaft with a gap; thedynamic pressure generating groove comprises a first dynamic pressuregenerating groove formed in at least either one of an outer periphery ofthe shaft and an inner periphery of the sleeve; the shaft body furthercomprises a shaft holder that holds a first end of the shaft; the shaftholder comprises a flange that holds the first end of the shaft, andfaces with a first end of the sleeve with a gap; the shaft furthercomprises a shaft flange that faces with a second end of the sleeve witha gap; and the dynamic pressure generating groove further comprises asecond dynamic pressure generating groove that is formed in at leasteither one of opposing surfaces of the shaft flange and the sleeve, andopposing surfaces of the sleeve and the flange; the shaft holder furthercomprises a flange encircling part that protrudes from an outerperiphery of the flange toward the rotator; the rotator comprises asleeve encircling part that is fastened to the sleeve in a mannerencircling the sleeve, and faces with the flange encircling part in theaxial direction with a gap, and, an extended part that extends from thesleeve encircling part toward the flange, and enters in the flangeencircling part; the shaft flange faces with an inner periphery of thesleeve encircling part with a gap in the radial direction; the extendedpart faces with an inner periphery of the flange encircling part with agap in the radial direction; the gap between the shaft flange and theinner periphery of the sleeve encircling part forms a first capillaryseal; and the gap between the extended part and the inner periphery ofthe flange encircling part forms a second capillary seal.
 2. The diskdrive device according to claim 1, wherein the first and second gapsform a bent labyrinth.
 3. The disk drive device according to claim 1,wherein a width of the first gap between the inner periphery of therotator and the opposing wall is equal to or greater than 0.05 mm and isequal to or less than 0.4 mm.
 4. The disk drive device according toclaim 1, wherein a width of the second gap between the end face of therotator and the chassis is equal to or greater than 0.02 mm and is equalto or smaller than 0.4 mm.
 5. The disk drive device according to claim1, further comprising a cap that is disposed on an upper face of therotator around the shaft so as to cover the first capillary seal,wherein: the shaft flange comprises an annular groove where a part ofthe cap enters; and a gap between the part of the cap and the grooveforms a bent labyrinth.
 6. The disk drive device according to claim 1,wherein: the chassis comprises a protrusion that encircles the flangeencircling part and protrudes toward the rotator; the sleeve encirclingpart faces with an inner periphery of the protrusion with a gap; and thegap between the sleeve encircling part and the flange encircling part,and the gap between the sleeve encircling part and the protrusion form acontinuous bent labyrinth.
 7. The disk drive device according to claim1, further comprising a communication channel that is formed in theouter periphery of the sleeve, and causes the first capillary seal andthe second capillary seal to be in communication with each other.
 8. Adisk drive device comprising: a chassis; a rotator that comprises a diskmount part, and an inner periphery to which a ring-shape magnet isfastened; and a fluid bearing unit that generates fluid dynamic pressureto a lubricant to support the rotator in a freely rotatable mannerrelative to the chassis, wherein: the rotator comprises a rotatoropposing face that faces with the chassis in an area outwardly in aradial direction with respect to an inner periphery of the magnet; thechassis comprises a chassis opposing face that faces with the rotatoropposing face with a first opposing gap; and a gas dynamic pressuregenerating groove that generates, when the rotator rotates relative tothe chassis, dynamic pressure in a pump-in direction to gas present inthe first opposing gap is provided in either one of the rotator opposingface and the chassis opposing face.
 9. The disk drive device accordingto claim 8, wherein: the rotator comprises a peripheral wall including aperipheral-wall end face that faces with the chassis in an axialdirection; the chassis comprises a thrust opposing face that faces withthe peripheral-wall end face in the axial direction with anaxial-direction gap; and a gas thrust dynamic pressure generating groovethat generates, when the rotator rotates relative to the chassis,dynamic pressure in the pump-in direction to gas present in theaxial-direction gap is provided in either one of the peripheral-wall endface and the thrust opposing face.
 10. The disk drive device accordingto claim 8, wherein: the rotator comprises an outer-periphery extendedpart that extends outwardly in the radial direction from an outerperiphery of the peripheral wall; the chassis comprises a radialopposing face that faces with an outer periphery of the outer-peripheryextended part in the radial direction with a radial-direction gap; andan outward gas radial dynamic pressure generating groove that generates,when the rotator rotates relative to the chassis, dynamic pressure inthe pump-in direction to gas present in the radial-direction gap isprovided in either one of the outer periphery of the outer-peripheryextended part and the radial opposing face.
 11. The disk drive deviceaccording to claim 8, wherein: the chassis comprises an opposing wallthat is formed annularly on a surface of the chassis at the rotatorside, and faces with at least partially an inner periphery of theperipheral wall in the radial direction with a second opposing gap; andan inward gas radial dynamic pressure generating groove that generates,when the rotator rotates relative to the chassis, dynamic pressure inthe pump-in direction to gas present in the second opposing gap isprovided in either one of the opposing wall and the inner periphery ofthe peripheral wall.
 12. The disk drive device according to claim 8,wherein: the chassis comprises a chassis recess that is an annularrecess provided around a rotation axis of the rotator, and comprises thechassis opposing face; and the rotator is provided with a cylindricalrotator entering part that comprises the rotator opposing face andenters the chassis recess.
 13. The disk drive device according to claim12, wherein: a thrust gap provided between an end face of the rotatorentering part and the chassis recess and extending in the radialdirection is equal to or greater than 0.02 mm and is equal to or smallerthan 0.4 mm; and a radial gap provided between an inner periphery of therotator entering part and the chassis recess and extending in the axialdirection is equal to or greater than 0.05 mm and is equal to or smallerthan 0.4 mm.
 14. The disk drive device according to claim 12, wherein aradial gap provided between an outer periphery of the rotator enteringpart and the chassis recess and extending in the axial direction isequal to or greater than 0.05 mm and is equal to or smaller than 0.4 mm.15. The disk drive device according to claim 8, wherein: the fluidbearing unit comprises a chassis-side gas-liquid interface of thelubricant exposed in an area between the chassis and the rotator; therotator comprises a rotator protruding part that encircles the fluidbearing unit, and extends toward the chassis; the chassis comprises achassis protruding part that encircles the rotator protruding part, andextends toward the rotator; and a gap between the rotator protrudingpart and the chassis protruding part extends in the axial direction, andforms a labyrinth that causes the chassis-side gas-liquid interface andthe opposing gap to be in communication with each other.
 16. The diskdrive device according to claim 8, wherein: the fluid beating unitcomprises a rotator-side gas-liquid interface of the lubricant exposedin an area of the rotator opened at a side apart from the chassis in theaxial direction; a cap is provided on an upper face of the rotatoraround the shaft so as to cover the rotator-side gas-liquid interface;an annular groove where a part of the cap enters is formed in the fluidbearing unit; and a gap between the part of the cap and the groove formsa bent labyrinth.
 17. A disk drive device comprising: a chassis; arotator that comprises a disk mount part, and an inner periphery towhich a ring-shape magnet is fastened; and a fluid bearing unit thatgenerates fluid dynamic pressure to a lubricant to support the rotatorin a freely rotatable manner relative to the chassis, wherein: therotator comprises a rotator opposing face that faces with the chassis inan area outwardly in a radial direction with respect to an innerperiphery of the magnet; the chassis comprises a chassis opposing facethat faces with the rotator opposing face with an opposing gap; a gasdynamic pressure generating groove that generates, when the rotatorrotates relative to the chassis, dynamic pressure in a pump-in directionto gas present in the opposing gap is provided in either one of therotator opposing face and the chassis opposing face; and the lubricantcontains an ionic liquid.